Jogging

I am working at the computer when Emily and Phoebe come jogging into the office, one behind the other. They make a turn behind my chair and leave. "One!" barks Emily in sergeant-majorly fashion. The sound of footsteps disappears.

Two minutes later they enter the room again and perform the same mini-circuit (in a space of about 2 square feet, forcing me to squeeze forwards out of their way). I notice as I turn to watch them leave the room that they are wearing wellington boots. "Two!" squeaks Phoebe.

When they return for a third time, I turn my chair to watch them. They are both dressed in red.

What is going on?